Electro-optical mixer

Abstract

The present invention discloses an electro-optical mixer (1) having an electrical signal output. The electro-optical mixer includes: a photodiode (PD), a first terminal and a second terminal, a ground terminal, a first matching network (Z2, Z4), a second matching network (Z1, Z3), a first decoupling element (C1), and a second decoupling element (C2); the photodiode is used to convert an incident optical signal; wherein, the first terminal can be connected to a first voltage source (V1) or a first current source (I1), the second terminal can be connected to a second voltage source (V2) or a second current source (I2), the ground terminal is used for the signal ground potential of the first voltage source (V1) and the second voltage source (V2); the first matching network is arranged on the anode side of the photodiode (PD), a part (Z2) of the first matching network is connected to the terminal of the second voltage source (V2) by a switchable switch (S2), another part (Z4) of the first matching network is connected to the ground terminal by another switchable switch (S2'), the second matching network is arranged on the cathode side of the photodiode (PD), a part (Z1) of the second matching network is connected to the terminal of the first voltage source (V1) by a switchable switch (S1), another part (Z3) of the second matching network is connected to the ground terminal by another switchable switch (S1'), the elements of the first matching network (Z2, Z4) and the second matching network (Z1, Z3) have inductive and / or resistive and / or capacitive characteristics, the first electrical decoupling element is arranged on the cathode side of the photodiode (PD), the second decoupling element is arranged on the anode side of the photodiode (PD), wherein, the first decoupling element (C1) and the second decoupling element (C2) have inductive and / or resistive and / or capacitive characteristics, and during operation, the first decoupling element (C1) and the second decoupling element (C2) output the electrical signal of the photodiode (PD).

Description

Technical Field

[0001] The invention relates to an electro-optical mixer. Background Art

[0002] In many cases, optical data is sent over long distances using optical fibers.

[0003] Optical fiber is also used in the radar field to distribute the local oscillator signal (LO).

[0004] In order to send data or radar signals wirelessly, the optical signal must be converted into an electrical signal before being up-converted.

[0005] The conversion of the optical signal to an electrical signal is performed using a transimpedance amplifier (TIA). The up-conversion to the desired RF frequency band is then performed using an electrical mixer.

[0006] The output signal from the TIA can then be further pre-processed using a DC-balanced buffer and a variable gain amplifier (VGA) before being multiplied by another signal using a mixer.

[0007] Figure 1 A block diagram describing the most relevant prior art is shown. In this case, an optical signal is routed from a switching center CO to an optical baseband receiver BPR via an optical fiber, where it is pre-processed (e.g., by processing methods using photodiodes, transimpedance amplifiers, DC-balanced buffers, and variable gain amplifiers (VGAs)), and then up-converted to the desired RF band (and another signal) using a mixer in an electrodialysis stage TX. In this case, the optical baseband receiver BPR and the electrodialysis stage TX are provided to, for example, a BICMOS integrated circuit.

[0008] In this process, both the transimpedance amplifier and the electrical mixer increase the complexity of the entire system.

[0009] In addition, the transimpedance amplifier needs to be approximately 0.25 mm 2 of separate chip area, which increases the cost of such a system.

[0010] In addition, each individual component has a certain bandwidth. By interconnecting these two components, the bandwidth of the entire system is determined by the bandwidth of the individual components and thus by the component with the lowest bandwidth. In order to detect high-frequency optical signals, a separate TIA must be used to minimize the effects of parasitic capacitance. This TIA generates additional noise.

[0011] These components also generate power losses, which impairs the efficiency of the system. Therefore, this solution is not suitable for low-power applications or battery-operated systems.

[0012] It should also be noted that providing the transimpedance amplifier as a separate component increases the risk of overall system failure.

[0013] In some applications, it may be desirable to use only specific frequency bands from any desired width of the optical signal. This is usually achieved using a filter after the TIA. This channel selection filter is based on passive components.

[0014] Assuming that real passive components always have parasitic resistance, the noise increases greatly.

[0015] Furthermore, the (passive) components require a large chip area, which significantly increases the system costs.

[0016] In some applications, it may be necessary to shut down a single unit while data signals and / or clock signals are still transmitted over the fiber to other systems.

[0017] There are a number of techniques that can be used to achieve this.

[0018] With the help of a Mach-Zehnder modulator (MZM) in front of the photodiode, the optical power at the photodiode can be set to zero individually. Figure 2 shown.

[0019] Here, the optical input signal from the laser diode LD is directed to the Mach-Zehnder modulator MZM. The output signal from the Mach-Zehnder modulator MZM is also optical and still has to be converted into an electrical signal using a photodiode PD. This electrical signal is then a current signal. For further processing, this current signal still has to be converted into a voltage signal in a transimpedance amplifier.

[0020] Given that the Mach-Zehnder modulator requires a considerable area and a very high control voltage, this solution is disadvantageous especially for integrated circuits and extremely scaled technologies.

[0021] A voltage in the range of 2-3 V is therefore required to control the Mach-Zehnder modulator. In modern transistors with dimensions in the nanometer range, this voltage range could already lead to failures of the driver components.

[0022] In addition, these driver components add to the mixer noise.

[0023] Furthermore, the MZM requires several square millimeters of chip area, which adds to the overall price of the system.

[0024] Finally, MZMs only have a bandwidth in the range <30 GHz, thereby making this solution unsuitable for HF applications.

[0025] As an alternative to the Mach-Zehnder modulator, the supply voltage can be switched off.

[0026] However, the disadvantage of this technology is that high currents must flow through the corresponding switching transistors. In order to compensate for the corresponding power dissipation in the transistors, cooling capacity must be planned, which greatly increases the system complexity.

[0027] As another alternative, one may choose to use an analog latch after the transimpedance amplifier to freeze the signal at a DC state.

[0028] However, analog latches are very expensive in the mm-wave range, which will significantly increase the system cost.

[0029] Furthermore, in known systems (wherever they are available) the matching networks are designed only as bandpass, so that it is generally not possible to select different frequency bands. Summary of the invention

[0030] It is an object of the present invention to specify a solution which avoids one or more problems of the prior art.

[0031] This object is achieved by an electro-optical mixer with an electrical signal output according to claim 1. Further advantageous embodiments of the invention are subject matter of the dependent claims, the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Embodiments of the present invention will be described by way of example with reference to the accompanying drawings, in which:

[0033] Figure 1 is an embodiment according to the prior art,

[0034] Figure 2 is another embodiment according to the prior art,

[0035] Figure 3 is a schematic diagram of an embodiment of the present invention;

[0036] Figure 4 is another schematic diagram of another embodiment of the present invention. DETAILED DESCRIPTION

[0037] The present invention will be described in more detail below with reference to the accompanying drawings. In this context, it should be noted that various aspects that can be used individually or in combination will be described. In other words, any aspect can be used together with various embodiments of the present invention, unless explicitly described purely as an alternative.

[0038] Furthermore, for simplicity, only one entity will be mentioned hereinafter as a rule. However, unless explicitly stated, the present invention may also include multiple related entities. In this context, the use of the words "a", "an" and "one" should only be understood to indicate the use of at least one entity in a single embodiment.

[0039] With regard to the methods described below, unless the context clearly indicates otherwise, the individual method steps may be arranged and / or combined in any desired order. Furthermore, unless clearly indicated otherwise, the methods may be combined with each other.

[0040] Generally, specifications with numerical values ​​are not to be understood as exact values, but include tolerances of + / - 1% to + / - 10%.

[0041] References to standards, specifications or guidelines should be understood as references to the standards, specifications or guidelines in force at the time of filing and / or also in force at the time of the priority application. However, this should not be understood as a general exclusion of the applicability of subsequent or replacement standards, specifications or guidelines.

[0042] Figure 3 and Figure 4 An electro-optical mixer 1 with an electrical signal output according to an embodiment of the present invention is shown.

[0043] The electro-optical hybrid 1 comprises at least one photodiode PD for converting an incident optical signal.

[0044] The electro-optical hybrid 1 further comprises at least one first terminal and at least one second terminal, whereby a first voltage source V1 can be connected (in each case) to the first terminal or to the respective first terminal and a second voltage source V2 can be connected (in each case) to the second terminal or to the respective second terminal.

[0045] Alternatively, the first energy source I1 can be connected (in each case) to the first terminal or the respective first terminal, and the second energy source I2 can be connected (in each case) to the second terminal or the respective second terminal.

[0046] The electro-optical hybrid 1 further comprises at least one terminal for a small-signal ground potential of the first voltage source V1 and the second voltage source V2. The small-signal ground potential may be any desired potential, but may in particular be the ground potential of the entire circuit.

[0047] The electro-optical hybrid 1 comprises a first matching network, denoted by Z2, Z4, which is arranged on the anode side of the photodiode PD, whereby a part of the first matching network (in this case Z2) is switchably connected to a terminal of a second voltage source V2 using a switch S2, and whereby another part of the first matching network (in this case Z4) is switchably connected to a terminal of a small-signal ground potential using a switch S2'.

[0048] The electro-optical hybrid 1 comprises a second matching network, represented by Z1, Z3, which is arranged on the cathode side of the photodiode PD, whereby a part of the second matching network (Z1 in this case) can be switchably connected to a terminal of a first voltage source V1 using a switch S1, and whereby another part of the second matching network (Z3 in this case) can be switchably connected to a terminal of a small signal ground potential using a switch S1'.

[0049] In this case, the matching network must have impedance matching, which means that the AC voltage isolation of a single capacitor (as a decoupling element) should not be understood as a matching network.

[0050] The components of the first matching network (in this case Z2 , Z4 ) and the second matching network (in this case Z1 , Z3 ) are characterized by inductive and / or resistive properties and / or capacitive properties.

[0051] The electro-optical hybrid 1 further includes a first decoupling element C1 disposed on the cathode side of the photodiode PD and a second decoupling element C2 disposed on the anode side of the photodiode PD.

[0052] The first decoupling element C1 and the second decoupling element C2 are characterized by having inductive and / or resistive characteristics and / or capacitive characteristics.

[0053] During operation, the first decoupling element C1 and the second decoupling element C2 output the electrical signal provided by the photodiode PD.

[0054] Using the above proposed device, a simple, space-saving and frequency-adjustable solution can be provided, which device can also be switched off.

[0055] In one embodiment of the present invention, the electrical signal outputs are fed to transimpedance amplifiers TIA1 and TIA2, respectively.

[0056] In another embodiment of the present invention, the switches S1 , S2 , S1 ′, S2 ′ are designed to be any desired switching elements selected as required, but in particular semiconductor switches, such as transistors.

[0057] According to one embodiment of the present invention, the electro-optical hybrid circuit can be operated as an optical receiver by selecting a switch given an appropriate switch selection.

[0058] According to yet another embodiment of the present invention, switches S1 , S2 , S1 ′, S2 ′ may be used to deactivate the electro-optical hybrid.

[0059] Without limiting the generality of the invention, the switch positions of the switches S1 , S2 , S1 ′, S2 ′ may be controlled by any desired signal, in particular by an optical signal and / or an electrical signal and / or a mechanical signal.

[0060] In one embodiment of the invention, the elements of the first matching network (in this case Z2 , Z4 ) and the second matching network (in this case Z1 , Z3 ) are characterized by inductive properties, whereby the inductive properties are provided by coils and / or lines.

[0061] In one embodiment of the invention, elements of the first matching network (in this case Z2, Z4) and the second matching network (in this case Z1, Z3) are alternatively or additionally characterized by capacitive properties, whereby the capacitive properties are provided by capacitors and / or lines.

[0062] Without limiting the generality of the invention, the electro-optical mixer circuitry is implemented in semiconductor technology (eg BiCMOS).

[0063] However, the mixer can also be realized using discrete components.

[0064] However, it is obvious that the electro-optical hybrid may also be partially integrated and, for example, comprise the individual elements as discrete components.

[0065] In all embodiments, it can be provided that the mixer can operate with any desired polarization light. The mixer can in particular operate with pure TE polarization light or with pure TM polarization light. The mixer can also operate with pure TE polarization light and pure TM polarization light and thus provide, for example, a process for polarization multiplexing.

[0066] exist Figure 3 In the embodiment shown, the optical signal RF is detected in the photodiode PD and converted into an electrical signal. The first matching network and the second matching network couple the output electrical signal and generate or select a frequency band through impedance matching provided by the first matching network and the second matching network.

[0067] exist Figure 3 In the example shown, the impedances Z1 ... Z4 are formed by inductors (however, not limited thereto), but the implementation of the impedances Z1 ... Z4 is not limited to coils and capacitors; other passive elements may also be used.

[0068] Since the anode and cathode impedances of the photodiode PD depend on the operating point, the channel / frequency band can be selected by varying the voltage V1, V2 or the current I1, I2, because for each different voltage the matching network formed by the first matching network and the second matching network interacting with the impedance of the photodiode PD becomes resonant with (other frequencies).

[0069] The actual mixing process is provided in the H-bridge consisting of S1, S2, S1', S2', Z1, Z2, Z3, Z4 and PD.

[0070] In the case where the voltage sources V1 and V2 each provide a voltage different from zero of large magnitude (compared to the small-signal ground potential), the following can be observed:

[0071] When switches S1 and S1 ′ are closed and the remaining switches are open, the photodiode PD is in a blocking direction and detects a dark current in addition to the photocurrent.

[0072] However, if switches S2 and S2' are closed and the remaining switches are open, the diode is in forward operation and the current is dominated by the diode current, with the result that the photocurrent is no longer detectable.

[0073] However, if the switches S1 ′ and S2 ′ are closed and the other switches are open, the bandwidth of the photodiode PD is reduced and thus only low frequency signals can be detected.

[0074] However, if switches S2 and S2' are closed (long term) and the remaining switches are open,

[0075] Then I 光电 < 二极管 In this case, Mixer 1 is turned off.

[0076] These explanations obviously also apply in a corresponding manner to the positive currents I1 , I2 which are each not zero.

[0077] Of course it should be noted that the description specified above is also valid in case the voltage sources V1 and V2 each provide a voltage less than zero (compared to the small signal quality potential), whereby the indices should be exchanged. Obviously, these explanations also apply correspondingly to negative currents I1, I2, each not being zero.

[0078] Figure 4 Another embodiment of the present invention is shown. In this case, the passive core remains, such as Figure 3 However, in case of very large capacitances, i.e. if C1, C2 → ∞, and the impedances Z1, Z2, Z3, Z4 (e.g. inductors) are chosen appropriately, broadband signals will also be detected.

[0079] In this case, the current can be converted to voltage using transimpedance amplifiers TIA1 and TIA2. However, if power is required at the output, the voltage can be converted to power at a specific impedance through an optional matching network (at the output of transimpedance amplifiers TIA1 and TIA2).

[0080] Furthermore, the mixer is not limited to just two transimpedance amplifiers (TIAs). Any desired number of TIAs sensitive to various frequencies may be used. S After selecting the appropriate transimpedance amplifier, channel selection can be performed.​

[0081] Figure 4 The illustrated embodiment allows for both wideband and narrowband operation.

[0082] In contrast to Gilbert cells or nonlinear components, the embodiments presented here utilize H-bridges. Furthermore, the mixer can be implemented as a broadband system or use channel selection. The mixer also provides a deactivatable option.

[0083] The electro-optical mixer according to the present invention includes an H-bridge that enables optical signals to be directly multiplied with electrical signals without the presence of a transimpedance amplifier. The electro-optical mixer according to the present invention consumes less power, has less complexity and less noise. The chip area is also reduced depending on the size of the TIA or Mach-Zehnder modulator. The bandwidth can be adjusted by using appropriate partial matching networks. Likewise, the bandwidth may be affected by the semiconductor technology used.

[0084] If transistors are used as switches S1, S2, S1', S2', this voltage (compared to a Mach-Zehnder modulator) should be sufficient to only reach >3U T (≈75 mV), which is significantly less than 2 V to 3 V.

Claims

1. An electro-optical mixer (1) having an electrical signal output, characterized in that: The electro-optical mixer comprises: • a photodiode (PD) for converting incident light signals; • a first terminal and a second terminal; The first terminal can be connected to a first voltage source (V1) or a first current source (I1), and the second terminal can be connected to a second voltage source (V2) or a second current source (I2). • a ground terminal for a signal ground potential of the first voltage source (V1) and the second voltage source (V2); • a first matching network (Z2, Z4) arranged on the anode side of the photodiode (PD), wherein a portion (Z2) of the first matching network is connected to a terminal of the second voltage source (V2) by a switchable switch (S2) and another portion (Z4) of the first matching network is connected to the ground terminal by another switchable switch (S2'); • a second matching network (Z1, Z3), which is arranged on the cathode side of the photodiode (PD), wherein a part (Z1) of the second matching network is connected to a terminal of the first voltage source (V1) by a switchable switch (S1), another part (Z3) of the second matching network is connected to the ground terminal by another switchable switch (S1'), and elements of the first matching network (Z2, Z4) and the second matching network (Z1, Z3) have inductive and / or resistive characteristics and / or capacitive characteristics; • a first decoupling element (C1), said first electrical decoupling being arranged on the cathode side of said photodiode (PD); • a second decoupling element (C2) arranged on the anode side of the photodiode (PD); The first decoupling element (C1) and the second decoupling element (C2) have inductance and / or resistance characteristics and / or capacitance characteristics, and during operation, the first decoupling element (C1) and the second decoupling element (C2) output the electrical signal of the photodiode (PD).

2. The electro-optical mixer according to claim 1, characterized in that: The output electrical signals are fed to transimpedance amplifiers (TIA1, TIA2) respectively.

3. The electro-optical mixer according to claim 1 or 2, characterized in that: The switches (S1, S2, S1', S2') are switch elements selected according to needs.

4. An electro-optical mixer according to any one of the preceding claims, characterized in that The switches (S1, S2, S1', S2') are semiconductor switches.

5. An electro-optical mixer according to any one of the preceding claims, characterized in that The electro-optical hybrid circuit can be operated as an optical receiver by selecting a switch.

6. An electro-optical mixer according to any one of the preceding claims, characterized in that The electro-optical mixer can be deactivated by means of the switches (S1, S2, S1', S2').

7. An electro-optical mixer according to any one of the preceding claims, characterized in that The switch positions of the switches ( S1 , S2 , S1 ′, S2 ′) can be controlled by any desired signals.

8. An electro-optical mixer according to any one of the preceding claims, characterized in that The switch positions of the switches ( S1 , S2 , S1 ′, S2 ′) can be controlled by optical signals and / or electrical signals and / or mechanical signals.

9. An electro-optical mixer according to any one of the preceding claims, characterized in that The component characteristics of the first matching network (Z2, Z4) and the second matching network (Z1, Z3) are inductance characteristics, wherein the inductance characteristics are provided by coils and / or lines.

10. An electro-optical mixer according to any one of the preceding claims, characterized in that The component characteristics of the first matching network (Z2, Z4) and the second matching network (Z1, Z3) are capacitive characteristics, wherein the capacitive characteristics are provided by capacitors and / or lines.

11. An electro-optical mixer according to any one of the preceding claims, characterized in that The mixer is realized in semiconductor technology.

12. An electro-optical mixer according to any one of the preceding claims, characterized in that The mixer is implemented using discrete components.

13. An electro-optical mixer according to any one of the preceding claims, characterized in that The mixer operates with light of any desired polarization.

14. An electro-optical mixer according to any one of the preceding claims, characterized in that The hybrid operates with pure TE polarized light and / or with pure TM polarized light.

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